MANCHESTER — Tuesday is election day, when voters will determine the outcome of 30 municipal races, including the ones for mayor and welfare commissioner, and whether to approve a slate of changes to the city charter, its basic governing document.

There are 50 candidates vying for the 28 seats on the boards of aldermen and school committee, including the four city-wide at-large seats. The welfare commissioner race pits 12-year incumbent Paul Martineau against Diane Guimond, the office's former deputy director.

The marquee race is between two-term incumbent Mayor Ted Gatsas and Patrick Arnold, the 30-year-old Ward 12 alderman. The two have clashed on a range of issues, foremost among them crime and education. Arnold, with his relatively light resume, is facing one of the state's best known political leaders, although his 40 percent showing in the primary surpassed expectations and the performance of Gatsas' past challengers.

Turnout in city elections has steadily declined over the past few decades, hitting a low in the last election of 28 percent. This year's primary saw an increase in turnout, from 8 percent in 2011 to 12 percent in September, so the increase may carry over to the general election. In any case, low turnout will likely benefit incumbents, who typically have a better chance of hanging on to their seats when voters stay home.

All but four aldermen and school board seats are contested. The incumbent at-large school board members, Kathy Staub and Dave Wihby, are the only two running for the seats.

One of the hardest fought and closely watched races is for Ward 10 alderman, pitting incumbent Phil Greazzo against Bill Barry, a former police officer.

In Ward 6, Alderman Garth Corriveau is being challenged by Joe Whitten, who has waged a vigorous campaign, and the race for Ward 12 alderman is a contest between two political veterans, Keith Hirschmann and Roger Beauchamp, the ward's current school board representative.

The race for welfare commissioner is a rematch between Martineau and Guimond, who lost by 900 votes in 2011. The Welfare Department has come under greater scrutiny since the last election. A legal advocacy group successfully challenged it in the state Supreme Court, and Martineau's salary, now $114,000, has also been criticized. Martineau has pointed out that his salary reflects his long tenure; the position enjoys set yearly raises under the Yarger Decker system.

Voters will also get to determine whether the welfare post remains an elected office. Having the commissioner be an appointed rather than an elected position is one of the nine changes proposed by the Charter Commission. Among the most significant charter revision proposals is to raise the mayor's salary to $100,000 a year and to eliminate the health and dental coverage for aldermen and school board members, while raising their stipends to $9,000 and $7,000 respectively.

The nine proposed revisions will be listed on the right side of the ballot. Voters will have the option of voting yes or no to the proposed revisions in their entirety.